1. Field of the Invention
The present invention generally relates to a semiconductor memory device. More specifically, the present invention relates to a semiconductor memory device with a redundant fuse circuit, such as Random Access Memory or other memory device.
This application is a counterpart of Japanese patent application, Serial Number 064487/1998, filed Feb. 27, 1998, the subject matter of which is incorporated herein by reference.
2. Description of the Related Art
In addition to increases memory capacities and memory densities being provided in a single chip, the semiconductor memory devices are also now provided with both redundant memory cells and normal memory cells. If a normal memory cell has a defect, the redundant memory cell is substituted for the defective memory cell. As a result, a faulty chip may be repaired or fixed. In this technical field, the technique mentioned above is widely used. A shift type redundant circuit is an example of a conventional technique.
A conventional circuit diagram is shown in FIG. 18. The conventional circuit has normal column lines CL0 to CL7 and redundant column lines RCL0 and RCL1. All the column lines are extended in the same direction (That is, the horizontal direction of FIG. 18) and separated from each other at regular intervals. The conventional circuit also has a fuse wiring path FL which includes four fuses F1 to F4. The fuse wiring path FL is extended in the vertical direction of FIG. 18, perpendicular to the horizontal direction.
In the conventional circuit, the intervals of the column lines must be reduced in order to increase the integration density. However, these intervals depend upon the size of the fuse that is extended in the vertical direction. That is, the fuse must have an appropriate area for use as the target of laser beams. Although it is desired to improve the integration density of the memory device, it is not a simple task to achieve this goal by reducing the fuse dependent intervals.
There has been a need for a semiconductor having an improved integration density.